In the past considerable attention has been given to various aspects of yarn store apparatus and methods, and numerous proposals have been advanced. Nevertheless, even further improvements still are being sought.
One area of interest relates to tension in the weft yarn when a picking movement is brought to an end abruptly. For example, in an air jet loom the weft yarn end is blown very rapidly across the shed, and the yarn movement ordinarily is stopped quite suddenly after the predetermined pick length has been inserted. The tension spikes which occur at such movements can be sufficiently high to damage the yarns and cause flaws in the weaving.
Another area of interest relates to controlling pick length, that is, to controlling the metering function of a yarn store so that reasonably fine adjustments in pick length can be made in response to sensed operating conditions in the loom. When a yarn store delivers too great a length for a perfect pick, the excess is wasted and may even cause a fault. When a yarn store delivers a length too short for a perfect pick, the integrity of the edge portion (selvage) of the fabric being woven may be affected adversely.
Of course, these factors also have to be considered within the context of many practical limitations which are placed upon the design of yarn stores for modern high speed looms. Speed and reliability of operation cannot be sacrificed materially in the search for more refined performance.